The Physics of Ski Jumping

From the moment the skier leaves the starting gate, he uses physics when he crouches down. Skiers who ski in speed competitions, or just people who ski for fun and want to go faster, also do this. When the skier crouches, he becomes aerodynamic because he makes the surface area of his body that is traveling through the air smaller and this causes air resistance to decrease. With less air resistance, he can go much faster and is able to obtain a larger speed before he jumps. As he travels down the hill, he gains speed because his gravitational potential energy from being at the top of the hill is converted into kinetic energy. Skiers can go extremely fast because the coefficient of friction between waxed skis and snow is 0.04, which is very low and this means that there is very little friction, also allowing the jumper to reach high speeds in the short amount of time he has to travel down the mountain before he jumps. Why is it important for the skier to go fast? The answer has to do with physics as well. As soon as the skier leaves the hill and is in the air, he is in free-fall because the only force acting upon him is gravity. He is moving in three dimensions, but we are only going to talk about two right now. In the x-direction, his speed remains constant from take-off point. In the y-direction, his speed is decreasing at a rate of 9.8 meters per second because of gravity. Gravity will pull him down at this rate no matter what because the x and y velocities do not affect each other at all. So, if he is going faster in the x-direction when he takes off, the skier will remain cover more distance before he is pulled back down by gravity.

This is the motion equation d=vit+(1/2)at2 that we have used before, with the additional y0. This y0 is included to compensate for the fact that a ski jumper’s jump starts higher up than it ends. That is, a ski jumper’s take off position is higher than the place it lands.

The second equation shows that, not including y0, or the initial height of the skier, is 11m. Supposing that the skier’s starting position was 90 m above his end position, the skier’s total vertical distance was 101 m. (roughly 331 feet)

The same physics apply when I try my hand at ski jumping (on a MUCH smaller scale).